title: Highly potent 5-aminotetrahydropyrazolopyridines: enantioselective dopamine D3 receptor binding, functional selectivity, and analysis of receptor-ligand interactions.
abstract: Heterocyclic dopamine surrogates of types 5 and 7 were synthesized and investigated for their dopaminergic properties. The enantiomerically pure biphenylcarboxamide (S)-5a displayed an outstanding K(i) of 27 pM at the agonist-labeled D(3) receptor and significant selectivity over the D(2) subtype. Measurement of [(35)S]GTPγS incorporation in the presence of a coexpressed PTX-insensitive G(α0-1) subunit indicated highly efficient G-protein coupling. Comparison of ligand efficacy data from cAMP accumulation and [(3)H]thymidine incorporation experiments revealed that ligand biased signaling is exerted by the test compound (S)-5a. Starting from the D(3) crystal structure, a combination of homology modeling and site directed mutagenesis gave valuable insights into the binding mode and the intermolecular origins of stereospecific receptor recognition. According to these data, the superior affinity of the eutomer 5a is caused by the favorable binding energy that results from interaction between the ligand's central ammonium unit and the aspartate residue in position 3.32 of the receptor.
authors.affiliation: Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich Alexander University, Schuhstrasse 19, D-91052 Erlangen, Germany.
authors.forename: Nuska
authors.initials: N
authors.lastname: Tschammer
authors.forename: Jan
authors.initials: J
authors.lastname: Elsner
authors.forename: Angela
authors.initials: A
authors.lastname: Goetz
authors.forename: Katharina
authors.initials: K
authors.lastname: Ehrlich
authors.forename: Stefan
authors.initials: S
authors.lastname: Schuster
authors.forename: Miriam
authors.initials: M
authors.lastname: Ruberg
authors.forename: Julia
authors.initials: J
authors.lastname: Kühhorn
authors.forename: Dawn
authors.initials: D
authors.lastname: Thompson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Whistler
authors.forename: Harald
authors.initials: H
authors.lastname: Hübner
authors.forename: Peter
authors.initials: P
authors.lastname: Gmeiner
mesh_terms: D057809:HEK293 Cells; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D011720:Pyrazoles; D011725:Pyridines; D050637:Receptors, Dopamine D3; C118531:pyrazolopyridine